Some internal combustion engines use turbochargers and other devices to improve their performance. A typical turbocharger includes a turbine, which is driven by exhaust gas, connected to a center housing, which in turn is connected to a compressor by a shaft running through the turbocharger that rotates during operation of the turbocharger and requires lubrication.
Lubrication for the turbocharger shaft is typically accomplished in the center housing by a flow of oil from the engine passing therethrough. The flow of oil usually is supplied by an oil pump attached to the engine. A series of tubes and passages usually fluidly connects an outlet of the oil pump with an inlet in the center housing. Oil drains from the center housing back into the engine.
When the engine is not operating, the oil pump does not supply oil to the center housing of the turbocharger, and most if not all of the oil in the center housing drains into the engine. When the engine is first turned on, the turbocharger shaft begins to rotate through the action of exhaust gas coming from the engine. As the engine begins to operate, the oil pump also begins to pump oil to various engine components, including the turbocharger. There is a lag time for oil from the oil pump before it reaches and lubricates the rotating shaft in the center housing of the turbocharger. This time lag may be attributed, in part, to factors such as the time required to prime the oil pump, travel time through the various tubes and passages connecting the oil pump and the center housing for the initial flow of oil, or high oil viscosity due to cold engine operation. During this lag time, the shaft in the center housing may be rotating without lubrication. This operation of the shaft without lubrication may cause scuffing or other damage of bearings attached thereon, a condition that may be exacerbated by high shaft rates of rotation. Many turbocharger manufacturers may specify a time frame within which a minimum oil pressure must be supplied to the turbo that may depend on the shaft's rotational speed.
Accordingly, there is a need for an apparatus and method for ensuring that adequate lubrication is available for a turbocharger shaft under conditions of initial engine startup or cold engine operation that ensures that adequate lubrication to the turbocharger is available when the engine is in operation.